1. Field of the Invention
This invention relates to an improved process for the preparation of xylazine. More particularly, the invention is directed to an improvement in the production of 2,6-dimethylphenylisothiocyanate an intermediate from which xylazine is prepared.
2. Description of the Prior Art
Xylazine, the well known sedative, analgesic, and muscle relaxant, has been produced by various alternate synthesis. One common synthesis can be summarized as follows: ##STR1##
In step 2 of this synthesis the organic solvent of choice in converting the amide first to the corresponding anion by the sodium hydride and then to the isothiocyanate by the addition to carbon disulfide is a 1:1 mixture of N,N-dimethylacetamide and benzene. See (a) I. Shahak and Y. Sasson, J. Am. Chem. Soc., 95, 3440 (1973). Unfortunately, even under the conditions considered optimum by the prior art, the highest yields of 2,6-dimethylisothiocyanate achievable have been on the order of 74-76 percent.